An adaptive filter is a filter that self-adjusts its transfer function according to an optimizing algorithm. Most adaptive filters are digital filters that perform digital signal processing and adapt their performance based on the input signals. An adaptive filter has adaptive filter coefficients. Adaptive filters are especially suitable to those applications where some parameters of the desired signal processing operation are not known in advance. Such applications commonly employ adaptive filters that use feedback to refine the values of their adaptive filter coefficients and hence their frequency responses. In general, the adapting process involves the use of a cost function, which is a criterion for optimum performance of the adaptive filter, to feed an optimizing algorithm, which determines how to modify the adaptive filter coefficients to minimize the cost of the next iteration. In contrast, a non-adaptive filter has static filter coefficients. Adaptive filters are routinely used in devices such as mobile telephones, digital cameras, camcorders, medical monitoring equipments, or tape drives for various purposes such as noise cancellation, signal prediction, adaptive feedback cancellation, or echo cancellation.
A tape drive is a data storage device that reads and writes data stored on a magnetic tape. It is typically used for offline, archival data storage. A tape drive may be connected to a computer through Small Computer System Interface (SCSI), Fibre Channel, Serial Advanced Technology Attachment (SATA), Universal Serial Bus (USB), FireWire, Fibre Connectivity (FICON), or other interfaces. A multichannel tape drive is capable of reading data from and writing data to multiple tracks on a magnetic tape simultaneously, thus providing a higher data transfer rate typically characterized by high tape speed, high tape capacity, and small tape thickness. Adaptive filters are often used in multichannel tape drives, and more specifically, in the read/write channels of the multichannel tape drives.